Archive for the 'Hill Climbs' category

What is Percent Grade

The term “grade” comes from civil engineering and is the most common method of specifying the sloop of a hill. By definition, grade is defined as:

It is not the angle of the hill, which is measured in degrees. A very steep section could be a 20% grade, which is about a 10 degree angle. A 45 degree angle would be 100% grade.

How Do We Use It?

There are two factors associated with a hill climb, the average grade and the grade at any given point. The average grade is easy to calculate, assuming you know the distance of the climb and the total elevation gain. Let’s take a hill that is 1 miles long with an elevation change of 1,000 feet (0.189 miles). You can calculate the grade as follows:

On our bikes we don’t actually measure the “run” but measure the road along the slope of the hill. Using a little trigonometry, we can determine that for this particular set of numbers the “run” is 0.98 miles and the grade is 19.2%. We could therefore use the measured distance on the bike and the error here would only be 2%, even less so for lower grades. We all know from climbing a very steep hill that a grade of 19% is very difficult, but none of the climbs we track have an average grade of 19%. The steepest of climbs usually average no more than 10% grade, or about 500 vertical feet per mile. In California, Bolhman On Orbit averages only about 10.5%. So although average grade is certainly a factor, there are several factors that need to be considered.

Maximum Grade

Total Distance

Total Elevation Gain

How each of these impact you as a climb is very much a personal thing. Some can power over a very steep, short section, and yet fade with a long climb, while others have a very difficult time with a short, steep grade (or maybe they are not using a low enough gearing) but can climb strong for 3,000 vertical feet.

Of all the parameters we could use to describe a hill climb, the hardest to determine is maximum grade. Unless you are a surveyor, you are usually limited to measuring elevation gain using an instrument that is using barometric pressure (or even less accurately, GPS only). How accurate is such a measurement? Pretty good over a significant elevation change, but not so good over a short distance. Couple that intrinsic error, with the aspect that a very short, but very steep pitch, is not nearly the same factor as a steep climb for 1/4 mile. So what are the parameters that should be used calculating maximum grade?

Last year I was biking in the beautiful island of Hilo Hawaii and ventured down about the steepest road I have ever attempted on a road bike. This is a view from the top that shows the vertical descent down to the ocean.

There was a sign at the top of the road that said 25% grade. This picture gives you the idea.

Going down was tough enough, going up was impossible and only one person in our group made it all the way up without stopping. To excuse myself for walking a section, I stopped and used an inclinometer application in my iPhone to measure the grade, resting in on the top tube. I measured 35% grade.

Does that mean the maximum grade was 35%? Even if the measurement device was accurate, it was still over a distance spanned by my two wheels so a bump in the road could have a big impact. To calculate the maximum grade, we need to decide over what distance. It is a decision that the designers of all cyclometers that read out percent grade, need to wrestle with. Make the distance too long and people don’t get the instant feedback they expect. Make it too short and you get some numbers that don’t reflect what you feel and that fluctuate too rapidly. So leave your comments here on:

What is the minimum distance we should use to calculator maximum grade.

How best to measure it.

We will use your feedback on developing some factor for maximum grade on the hills we track.

Website Changes

We are updating our hill climbs on the Ultra Cycling website (http://www.ultracycle.net). We are working on maps and hill profiles for the various climbs. Look for those changes to be coming soon.

For those who live in the bay area and want to test their climbing skills on some of the local favorites, the 2010 Low Key Hill Climb schedule has been announced. These have had a large turn out and you can make up your own category. Many of the climbs that are planned are also on the Ultra Cycling King of the Mountain hills, so you can have a chance to enter your times here.

The links under the Low Key Hill Climb column take you to their website. The links under the Ultra Cycling KOM Equivalent column are for the Ultra Cycling website KOM times for that hill. Note that for the Ultra Cycling website we only include times that individuals input and do not enter any data from the LKHC or other races.